Increased plasma vasopressin and serum uric acid in the low renin type of essential hypertension

Plasma vasopressin in hereditary cranial diabetes insipidus

A family comprising 46 members of 4 generations is described; 21 members suffered from incomplete diabetes insipidus (DI) of central origin. The pedigree showed a dominantly transmitted condition. The onset is gradual and starts in early infancy. The clinical symptoms are highly variable and decline in the sixth decade. Plasma vasopressin (AVP) during water deprivation was significantly lower in the DI group than in the controls (4.2 +/- 0.5 vs. 10.6 +/- 1.7 ng/l) (p less than 0.01), the difference being more pronounced in the high osmolality range (4.8 +/- 0.7 vs. 14.4 +/- 3.1 ng/l) (p less than 0.01). Urine osmolality was lower (241 +/- 36 vs. 928 +/- 46 mOsm/kg H2O) (p less than 0.01) despite higher serum osmolality during water deprivation, rendering the ratio between urine and serum osmolality less than unity compared with greater than 3:1 in the control group (p less than 0.001). In two affected females, addition of a non-osmotic stimulus caused no increase in plasma AVP. The findings are consistent with a partial defect in the production or release of AVP and not with a dysfunction of the intracranial osmoreceptors. The variable features of incomplete DI indicate that to define the condition by excessive urinary output alone is insufficient. The ratio between urine and serum osmolalities after an appropriate osmotic stimulus together with plasma AVP measurements may be necessary to confirm the diagnosis.

Abnormal vasopressin and aldosterone response to furosemide in essential hypertension

Plasma concentrations of arginine vasopressin (AVP), angiotensin II (AII), aldosterone (Aldo), urinary output (V), osmolar clearance (Cosm), free water clearance (CH2O), fractional excretions of sodium (FENa) and potassium (FEK), urinary sodium excretion rate (U-Na) and serum potassium (S-K) were determined in 9 patients with essential hypertension (group I) and 13 normotensive healthy control subjects (group II) before and three times during the first 4 hours after an intravenous injection of 40 mg of furosemide. AVP, AII, Aldo, V, Cosm, FENa, FEK and U-Na increased in both groups. However, the elevation in AVP was significantly more pronounced and the rate of increase in Aldo was significantly slower in group I than in group II. There were no significant differences in AII, V, Cosm, CH2O, FENa, FEK and U-Na between the groups. S-K was significantly reduced only in group I. AVP and AII were not significantly correlated to each other or to blood pressure. It is suggested that the responsiveness of the renal tubules to AVP is reduced in essential hypertension and that the larger increase in AVP might be a compensatory phenomenon. The slower increase in Aldo in essential hypertension could be attributed to the reduction in S-K.

The effect of sodium depletion and potassium supplementation on vasopressin, renin and catecholamines in hypertensive men

Seventeen 50-year-old hypertensive men (157 +/- 4/110 +/- 2 mmHg, mean +/- SE) were given low sodium diet for one week, which was supplemented with potassium the following week. The urinary Na+/K+ excretion ratio changed from 2:1 to 1:5 and 1:12, respectively, during dietary intervention. Arterial plasma vasopressin decreased by 3.4 +/- 1.7 ng/l (0.05 less than p less than 0.10) and urinary excretion of vasopressin was reduced by nearly 50% (p less than 0.001) during sodium depletion, while plasma noradrenaline increased by 38% (p less than 0.001) and plasma dopamine showed an increase by 58% (p less than 0.001). Plasma renin concentration increased four-fold during sodium depletion (p less than 0.001). With combined salt depletion and potassium supplementation, arterial plasma vasopressin decreased by 9.5 +/- 4.0 ng/l (p less than 0.05) compared to control. Urinary excretion of vasopressin together with plasma noradrenaline and dopamine were unchanged during the second week. The reduction of blood pressure was most marked during the first week (143 +/- 3/103 +/- 2 mmHg, p less than 0.05), but continued to fall also during the second week. Thus, during sodium restriction in middle-aged hypertensive men, blood pressure reduction occurs concomitantly with inhibited vasopressin release, despite enhanced renin and catecholamine release. Potassium supplementation during sodium restriction induces only minor changes in these variables.

Heat stroke in endurance exercise

Six athletes were examined immediately after collapsing from heat stroke during exercise, and then followed for several weeks. At the time of collapse most of the patients were sweating profusely, their rectal temperatures being more than 42 degrees C. All recovered within a few hours. The renal function was not disturbed more than expected during heavy exercise, serum levels of liver enzymes were, however, increased for several weeks. Electrolyte homeostasis was undisturbed but for a transient hypercalcemia that can not be fully explained. The marked increments in plasma levels of catecholamines, vasopressin and renin were as expected after heavy exercise. We conclude that as heat stroke presents as a continuum of clinical pictures, biochemical evidence of liver cell injury is a sensitive and important parameter for the diagnosis.

Vasopressin receptor antagonists: pharmacological tools and potential therapeutic agents

The present survey deals with the development and applications of non-peptidergic vasopressin receptor antagonists. The existence of at least three vasopressin receptors (V(1), V(2) and V(3) respectively) is firmly established. V(1)-receptors play a relevant role in the regulation of vascular tone, whereas V(2)-receptors are known to mediate the antidiuretic activity of vasopressin at the level of the renal collecting ducts. The V(3)-receptor appears to be involved in the release of the adreno-corticotropic hormone. Vasopressin receptor antagonists which are peptides have been known for several decades, more recently, both V(1)- and V(2)-receptor blockers which are non-peptidergic have been introduced, as well as agents with affinity for both V(1)- and V(2)-receptor subtypes. A survey of these non-peptidergic antagonists is presented here. Such compounds are useful as pharmacological tools, and they can also be thought of as therapeutic agents as therapeutic agents in cardiovascular and renal diseases. Selective V(1)- and V(2)-receptor antagonists were used to study the interaction between vasopressin receptors and sympathetic neurones. Depending on the experimental model used this interaction can occur at either the pre- or postsynaptic sites. In both cases predominantly V(1)-receptors are involved. A brief survey is given of the potential use of V-receptor antagonists in the drug therapy of syndrome of inappropriate antidiuretic hormone secretion and other water retaining disorders, congestive heart failure and certain forms of hypertension (in particular in the Negroid hypertensive patients).

Abnormalities in hypothalamic and neurohypophysial vasopressin content are not a consequence of hypertension in the spontaneously hypertensive rat

In order to determine if the decreased hypothalamic and increased posterior pituitary content of vasopressin (VP) observed previously in spontaneously hypertensive rats (SHR) were a secondary consequence of the hypertension, the effect of preventing the development of hypertension on VP content of the hypothalamoneurohypophyseal system was evaluated. Two methods for preventing the hypertension were used: (1) chronic angiotensin-converting enzyme inhibition (oral captopril, 100 mg/kg/day at 4-12 weeks of age); and (2) intraventricular 6-hydroxydopamine (6-OHDA, 200 micrograms at 4 and 5 weeks of age). Both of these treatments markedly attenuated the increase in systolic blood pressure in SHRs at 5-11 weeks of age. The captopril-treated rats had a significant elevation in serum renin activity at 12 weeks of age indicating the presence of chronic converting enzyme inhibition, and the 6-OHDA-treatment resulted in a depletion of hypothalamic (86%) and brainstem (76%) norepinephrine content. Hypothalamic VP content was reduced in untreated SHRs compared to normotensive Wistar-Kyoto rats (WKYs, P = 0.0015). It was not significantly altered in either strain by the 6-OHDA treatment. Captopril caused a reduction in hypothalamic VP content in both SHRs and WKYs (P less than 0.01). Posterior pituitary VP content was elevated in untreated SHRs compared to WKYs (P less than 0.001), and remained elevated with captopril and 6-OHDA treatments. These data indicate that the abnormalities in VP content in the hypothalamus and posterior pituitary of SHRs are not a response to the hypertension. Therefore, they may represent primary abnormalities in the SHR.(ABSTRACT TRUNCATED AT 250 WORDS)

Aging and urinary vasopressin excretion in healthy men

The influence of age on urinary excretion of arginine vasopressin (antidiuretic hormone) was examined in three groups of healthy men, 25 +/- 1 (n = 12), 40 (n = 44) and 50 years of age (n = 28) respectively. Despite increasing plasma vasopressin with progressive age (2.5 +/- 0.6 vs. 3.5 +/- 0.4 vs. 7.4 +/- 1.0 ng/l, respectively) (means +/- SE), urinary excretion of vasopressin turned out similar (6.7 +/- 1.0 vs. 6.8 +/- 0.8 vs. 6.9 +/- 0.6 ng/h). No differences in sodium excretion, serum osmolality and creatinine clearance appeared that could explain these findings. The present results suggest that age-related impairment of renal concentrating capacity is compensated for by increasing circulating plasma vasopressin. Furthermore, differences in tubular handling of the hormone with age may explain the present findings, and may be another compensatory mechanism for decreased urinary concentrating ability.

Differential pulse voltammetry in vivo with working carbon fiber electrodes: 5-hydroxyindole compounds or uric acid detection?

Differential pulse voltammetry was performed in rats chronically implanted with carbon fiber electrodes in the caudate (n.Cd) and raphe dorsalis (n.RD) nuclei. The electrochemical signal obtained at the +300 mV potential (peak 3) in animals implanted for more than one week (long term chronic conditions, greater than 7 days) could be dependent upon the extracellular fraction of 5-hydroxyindolacetic acid (5-HIAA) since a single injection of Pargyline is sufficient to suppress it in n.Cd and n.RD. This result was obtained despite the tendency of Pargyline to increase n.Cd and n.RD endogenous concentrations of Uric Acid (UA) measured by High Performance Liquid Chromatography (HPLC). In contrast, in animals implanted for less than one week (short term chronic conditions, less than 7 days) peak 3 recorded in the same structure could be dependent upon extracellular fractions of 5-HIAA and UA since consecutive injections of Pargyline and Allopurinol are necessary to suppress this signal. The source of extracellular UA measured in brain by voltammetry, in such short term chronic conditions, might result from surgical trauma.

Effect of exercise on plasma concentrations of arginine vasopressin, angiotensin II and aldosterone in hypertensive and normotensive renal transplant recipients

Plasma concentrations of angiotensin II (A II), aldosterone (Aldo) and arginine vasopressin (AVP), and serum osmolality (Sosm) were determined before and after gradually increasing exercise loads on a bicycle ergometer in 10 hypertensive (group I) and 10 normotensive renal transplant recipients (group II), and in 15 healthy control subjects (group III). Working capacity was reduced in groups I and II. The A II, Aldo, AVP, Sosm increased in all groups after exercise. The A II was higher in group I than II and the percentage changes were significantly lower in groups I and II than in group III. There were no significant differences in Aldo between the groups either before or after exercise. The AVP was the same in groups I and II, and AVP in these groups was higher than in group III. The Sosm and AVP were significantly correlated in all groups. Neither A II, Aldo nor AVP were significantly correlated to systolic blood pressure (BP). Alterations in AVP, but not in A II or Aldo, were correlated to the degree of exercise load. It can be concluded that the renin-angiotensin-aldosterone system and the osmoregulatory system are stimulated during exercise in renal transplant recipients. The A II is elevated in post-renal transplant hypertension, but the responsiveness is reduced in both hypertensive and normotensive recipients. The alterations in AVP are probably secondary to changes in Sosm, and the higher AVP levels in recipients could be due to a decreased responsiveness of the renal tubules to AVP. Our findings are in good agreement with the hypothesis that hypertension after renal transplantation is angiotensin II-dependent.

The osmoregulatory system and the renin-angiotensin-aldosterone system in pre-eclampsia and normotensive pregnancy

Plasma concentrations of arginine vasopressin (AVP), angiotensin II (A II), aldosterone (Aldo), serum osmolality (Sosm), urine volume (V), and free water clearance (CH2O) were determined in the third trimester of pregnancy, and 5 days and 3 months after delivery in pre-eclampsia (group I), in normotensive pregnancy (group II), and in non-pregnant control subjects (group III). The AVP was the same in the third trimester of pregnancy in groups I and II and did not deviate significantly from the level in group III. However, 5 days after delivery, AVP was lower and V and CH2O higher in group I than in group II. There was no correlation between AVP and Sosm in the third trimester in either group I or II, but 5 days after delivery a significant positive correlation was found between these parameters in both groups I and II as well as in group III. The A II and Aldo changed qualitatively in the same way in groups I and II, that is, considerable elevation in the third trimester and normalization after delivery. Also, A II and Aldo were lower in group I than in II. The AVP and A II were not correlated and there was no significant relationship between systolic or diastolic blood pressure on the one hand and AVP, A II or Aldo on the other in either group I or II. Thus the osmoregulatory system appears to be altered in both pre-eclampsia and normotensive pregnancy, but becomes normal again 5 days after delivery. In pre-eclampsia a suppression of AVP seems to be responsible for the elimination of excess water in pre-eclampsia 5 days after delivery. There was no evidence for a causal relationship between blood pressure and the osmoregulatory system or the renin-angiotensin-aldosterone system in any of the pregnant groups.

Sex differences in the endocrine predictors of essential hypertension. Vasopressin versus renin

The relationships between arterial pressure (BP) and plasma vasopressin levels, plasma renin activity, and other variables were determined in 96 untreated essential hypertensive men (146/100 mm Hg) and women (153/102 mm Hg) whose average age was 44 years, 80 normal men and women (121/79 mm Hg; mean age, 47 +/- 2 years), and 40 subjects defined as borderline hypertensive. An analysis of variance indicated significant sex differences in the population. Levels of plasma vasopressin were significantly elevated in hypertensive men, with 26% (high plasma vasopressin hypertensive) exhibiting levels greater than 2 SD of the normal mean, and multivariate regression analysis indicated a significant positive correlation between plasma vasopressin levels and systolic and diastolic blood pressure. Hypertensive men had a larger daily urine volume than normal men. Diastolic pressure and heart rate were significantly elevated in a subgroup of 12 weight-matched and age-matched hypertensive men in the high plasma vasopressin group compared with levels in normal plasma vasopressin hypertensive men. Hypertensive women had lower plasma renin activity than normal women, and multivariate analysis indicated a significant negative correlation between plasma renin activity and systolic and diastolic blood pressure. Other significant abnormalities in both sexes were noted: hypertensive men and women weighed more and excreted more sodium per day, and both had higher heart rates. With a discriminant analysis of 18 variables in male subjects, plasma vasopressin levels, urinary sodium excretion, and heart rate correctly classified 71% of normal and hypertensive subjects. In women, plasma renin activity, urinary sodium excretion, and heart rate correctly classified 77% of normal and hypertensive subjects. Despite the inability to ascertain causal relationships, the ability of the three variables in combination to correctly classify normal and hypertensive subjects indicates that these combined variables are reproducibly altered in persons with essential hypertension.

Evidence of age-related variation in plasma vasopressin of normotensive men

The influence of age on plasma arginine vasopressin was examined in three groups of healthy men, 25 +/- 1 (n = 12), 40 (n = 23) and 50 years of age (n = 13), respectively. The three groups were comparable in body height, weight, blood pressure, heart rate, serum and urine osmolality, electrolytes and endogenous creatinine clearance. Compared to the 25-year olds, the 50-year old men had more than three times higher basal plasma vasopressin (7.8 +/- 1.4 vs. 2.5 +/- 0.6 ng/l, p less than 0.01), only one-third the plasma renin concentration (0.36 +/- 0.05 vs. 1.10 +/- 0.33 G.U. X 10(-4)/ml, p less than 0.01) and a significantly higher plasma noradrenaline (267 +/- 21 vs. 199 +/- 19 ng/l, p less than 0.05) while plasma adrenaline remained essentially unchanged. The 40-year olds had intermediate plasma vasopressin concentrations (4.2 +/- 0.6 ng/l). Thus, age is a variable with a substantial effect on plasma concentrations of vasopressin in addition to the well-known effect on renin and noradrenaline. Age must be taken into account in further clinical studies on vasopressin.